iOS targets appear to not work

[nagisa]

Did not investigate too closely yet, filling so I don’t forget.

Goal is to run tests for all the iOS targets.

• aarch64-apple-ios: when running cross --test, error: could not execute process (never executed)
• armv7-apple-ios: when running cross --build, ld: library not found for -lcrt1.3.1.o
• armv7s-apple-ios: when running cross --build, ld: library not found for -lcrt1.3.1.o
• i386-apple-ios: when running cross --build, ld: building for OSX, but linking against dylib built for iOS (/Applications/Xcode-9.4.1.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator11.4.sdk/usr/lib/libobjc.tbd). file '/Applications/Xcode-9.4.1.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator11.4.sdk/usr/lib/libobjc.tbd' for architecture i386
• x86_64-apple-ios: when running cross --build, ld: building for OSX, but linking against dylib built for iOS (/Applications/Xcode-9.4.1.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator11.4.sdk/usr/lib/libobjc.tbd). file '/Applications/Xcode-9.4.1.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator11.4.sdk/usr/lib/libobjc.tbd' for architecture x86_64

[nagisa]

(Note: specifically did not fill against cross, because it does not list these targets as supported, while trust does)